This disclosure relates to an upstream portion of a diffuser sometimes referred to as a “pre-diffuser.” More particularly, the disclosure relates to struts on the pre-diffuser and fluid flow therethrough.
A gas turbine engine typically includes a fan section, a compressor section, a combustor section and a turbine section. Air entering the compressor section is compressed and delivered into the combustion section where it is mixed with fuel and ignited to generate a high-speed exhaust gas flow. The high-speed exhaust gas flow expands through the turbine section to drive the compressor and the fan section.
Historically, a fan in the fan section was driven at the same speed as a turbine within the turbine section. More recently, it has been proposed to include a gear reduction between the fan section and a fan drive turbine. With this change, the diameter of the fan has increased dramatically and a bypass ratio or volume of air delivered into the bypass duct compared to a volume delivered into the compressor has increased. With this increase in bypass ratio, it becomes more important to efficiently utilize the air that is delivered into the compressor section.
One factor that increases the efficiency of the use of this air is to have a higher pressure at the exit of a high pressure compressor. This high pressure results in a high temperature increase. The temperature at the exit of the high pressure compressor is known as T3 in the art. T3 air is sometimes used to cool the turbine section, for example, through a tangential on-board injector (TOBI), as well as provide air for other uses in the engine. Due to the increased T3 temperature, super-cooled fluid from a heat exchanger has instead been provided to the TOBI and other engine areas.